1. Field of the Invention
This invention relates to a hydraulic, adjustable shock absorber, in particular for motor vehicles, such a shock absorber having a work cylinder, a piston fastened to a piston rod and dividing the work cylinder into two work chambers, at least one additional surrounding tube coaxial to the work cylinder and at least one adjustable damping valve located in a stationary and sealed manner on the side of the shock absorber, whereby a centering ring fixes the damping valve.
2. Background Information
Known are hydraulic, adjustable shock absorbers, such as disclosed in Federal Republic of Germany Patent No. 41 37 330, in which a work piston fastened to a piston rod divides the work cylinder into two work chambers, and in which there is at least one adjustable control valve located on the side of the shock absorber. To form a bypass and for the inflow of the controllable damping valve, there is an additional tube outside the work cylinder but inside the jacket tube which forms the equalization chamber. The valve cartridge runs through a form-fitted centering ring and is connected to the additional tube by means of a threaded coupling. The centering ring is sealed against the atmosphere both by means of its shape, which shape corresponds to the shape of the outer tube, and by an additional gasket.
One disadvantage of this known design is that the threaded coupling between the valve cartridge and the additional tube can exert a torque bias on the work cylinder, so that there can be problems regarding the free movement of the work piston. Such a threaded coupling between the valve cartridge and the additional tube is essentially only possible if the oil conductor is supported in the vicinity of the piston rod guide or of the valve base. Such a support has the additional disadvantage that an excessively long oil conductor reduces the size of the equalization chamber, in which case either this equalization chamber has to be enlarged or, if the equalization chamber is too small, a foaming of the damping medium can occur.
Also known are shock absorber systems for vehicles, such as that disclosed in Federal Republic of Germany Patent No. 35 35 287, FIG. 2, in which a prefabricated thick-walled pipe base is welded to he outer tube of the shock absorber. One advantage of this configuration is that the valve cartridge is isolated from the oil conductor, which means that the valve cartridge and the oil guide tube can move relative to one another, which means that there is essentially no reason to fear a torque bias on the work cylinder. But this design has the disadvantage that the pipe base typically must be manufactured as a complex lathe-turned and/or milled part. The subsequent welding of the pipe base to the jacket tube requires refinishing work, since the parts which fit together and their fastening threads are located in the immediate vicinity of the weld seam.